Glossary
Needle shut-off
Definition
Safety function that closes the fuel path into the combustion chamber with a needle when the burner is switched off.
Needle shut-off is the safety function that prevents fuel from entering the combustion chamber after the burner has been switched off. It is realised by a needle that seats on the nozzle orifice or by a valve on the lance, actuated hydraulically by the fuel pressure (types H and EH) or pneumatically (type HA).
The function is a safety device, not a convenience feature: it is what stops the oil train from dripping into a hot furnace during the post-purge period. In the European market such devices are certified against DIN EN ISO 23553-1.
Fluid Control Instruments Ltd atomizers and lances form one certified unit. The atomizer may carry the needle itself (TYPE 32 spill-back, most disc and air/steam executions), or the lance may carry it and the atomizer may be supplied without a needle (TYPE 9). The certification applies when original Fluid Control Instruments Ltd atomizers or atomizer parts are used with the lance.